A plasma processing system for performing plasma processing on a substrate, e.g., a semiconductor wafer (hereinafter, simply referred to as “wafer”) includes a process module serving as a vacuum plasma processing chamber, and a loader module serving as an atmospheric transfer chamber for loading and unloading the wafer into and from a container, e.g., a front opening unified pod (FOUP), accommodating a plurality of wafers.
In the plasma processing system, the wafer is unloaded from the FOUP connected to a container connecting mechanism (load port) of the loader module and then loaded into the process module through the loader module, a load-lock module serving as an atmosphere/vacuum switchable chamber and a transfer module serving as a vacuum transfer chamber.
In consideration of the plasma process efficiency, the plasma processing system generally includes a plurality of process modules. Therefore, the loader module has a plurality of, e.g., three, load ports to simultaneously load wafers into the respective process modules. The load ports are arranged linearly on one side surface of a housing-shaped loader module (see, e.g., Japanese Patent Application Publication No. 2006-261456).
Recently, the number of process modules of the plasma processing system increases in view of throughput improvement. For example, there is developed a plasma processing system including six process modules. In such a plasma processing system, different processes may be performed in the respective process modules depending on the modes of the respective process modules. Specifically, the process modules and wafer lots are made to correspond to one another, and each of the process modules may process only wafers in a lot corresponding thereto. In that case, wafers are transferred between a load port and a single process module without being sequentially transferred between the process modules. Thus, in order to minimize a period of time during which the process modules are being empty, load ports are preferably provided such that the number of the load ports is equal to or greater than the number of process modules. In the above plasma processing system, it is preferable that the loader module has at least seven load ports.
However, in the case of arranging at least seven load ports linearly on one side surface of the loader module, a foot print of the loader module is increased, which makes it difficult to install the plasma processing system in a clean room. Especially, scaling up of a wafer diameter, specifically, from 300 mm to 450 mm, is expected, so that the problem of the increase in the foot print of the loader module becomes more significant.